Interactions between Daphnia parasites: effects of arrival order, spore dose, and host age
|Date||22 April 2021|
Prof. Meghan Duffy (Ecology and Evolutionary Biology, University of Michigan)
Most populations host multiple parasites. These co-occurring parasites interact within individual hosts and at the host population scale. This has consequences for host and parasite fitness, as well as for community-level host-parasite dynamics. A current challenge is to uncover the mechanisms driving these interactions between parasites, which will allow us to understand and predict the dynamics of host-multiparasite systems. In this talk, I will present the results of studies on Daphnia and two of their common parasites in which we considered three factors that can influence interactions between parasites. We first studied the influence of arrival order on coinfecting parasites. In laboratory studies, we found that parasites had increased fitness in coinfected hosts when they were the second parasite to infect a host, compared to when they were the first parasite to infect a host. We then analyzed an epidemiological model with priority effects to understand when priority effects increase parasite coexistence, and when they decrease coexistence. Moreover, we identified the natural conditions under which we expect within-host priority effects to foster coexistence in our system. The second study tested how changing the transmission spore dose to which hosts are exposed influences coinfection. We found that the likelihood of coinfection was an additive function of both parasite dose-response relationships, resulting in a non-monotonic response surface with the highest likelihood of coinfection centered around moderate doses of both parasites. Finally, we tested the impact of host age on interactions between parasites, finding that within-host interactions between parasites weakened as hosts aged. Using an epidemiological model, we found that these age effects created epidemiological feedback loops that increased the negative impact of coinfection on one parasite and decreased the positive impact of coinfection on the other parasite. Together, these findings show that we can better understand host-multiparasite systems by carrying out studies aimed at uncovering mechanisms driving their interactions, rather than studying them phenomenologically.
The IBED seminar will take place online via Zoom: https://uva-live.zoom.us/j/84258968254